Part 4/15:
His observations revealed that the Moon’s surface was not smooth but covered with mountains and craters, contradicting Aristotle’s assertion of perfect celestial spheres made of pure ether. Galileo also observed the four largest moons orbiting Jupiter—an unmistakable proof that not everything revolved around Earth. This discovery hinted strongly that Earth was not the universe's center, laying groundwork for the heliocentric model later refined by Copernicus.